1. Field of the Invention
This invention relates to a volume control circuit suitable for use, in particular, in an AV (audio/video) system in which an 8 mm VTR deck and a tuner are separate components.
2. Description of the Prior Art
A video composite system has been proposed in which an 8 mm VTR deck, a liquid crystal color monitor, and a tuner are prepared separately and can be combined to set up an Av system. Such a video composite system allows various usage users may desire, such as, not only using it as a small-scaled AV system but also using the 8 mm VTR deck alone for edit purposes, and using the 8 mm VTR deck with a video camera connected. Additionally, speakers with a built-in amplifier may be coupled to the 8 mm VTR deck to set up an AV system for full-scale audio reproduction.
If the video composite system is equipped with a remote commander for channel changeover, volume adjustment and so on, it will be convenient to use an AV system which is made thereof. The 8 mm VTR deck of the video composite system is often used as a separate portable device whereas the tuner is normally used in a stationary condition in a room or a car. For this reason, an optical sensor of the remote commander is provided in the tuner.
When the optical sensor of the remote commander is provided in the tuner, it is easy to arrange the system to permit channel changeover through the remote commander. By coupling the tuner and the 8 mm VTR deck via a general digital signal conductor, it is also relatively easy to arrange the system to select a mode of the 8 mm VTR through the remote commander.
If the optical sensor of the remote commander is provided in the tuner, it is difficult to control the audio output level of the VTR deck. More specifically, in order to control the audio output level of the 8 mm VTR deck, it is necessary to equip the 8 mm VTR deck with an electronic volume control variable in gain according to a value set and to connect the electronic volume control of the 8 mm VTR deck and a system controller of the tuner having the optical sensor of the remote commander via a particular signal conductor. This, however, requires the particular signal conductor for connection between the 8 mm VTR deck and the tuner, and hence increases the number of connectors and makes it difficult to decrease the size of the system.
When a full-scale Av system is set up by connecting speakers with a built-in amplifier to the 8 mm VTR deck, it is strongly desired to allow volume adjustment through a remote commander.